1. Field of the Invention
The present invention relates to a manifold valve for properly supplying secondary fluids into a primary fluid.
2. Description of the Related Art
In some factories, a primary fluid such as pure water is supplied to a work site, and depending on the work or products at the work site, secondary fluids, in prescribed quantities, are selected and added to the primary fluid. FIG. 4 shows a manifold valve 30 used for this purpose and arranged in the middle of piping for supplying the primary fluid to the work site. FIG. 5 is a sectional view taken along a line 5--5 of FIG. 4. For the sake of clear understanding, the sectional view of FIG. 5 cuts across air ports 43 and 44 for vertically driving a valve element 41 of a valve unit 40, and therefore, does not correctly follow the line 5--5 of FIG. 4.
The manifold valve 30 consists of a base block 31 of a rectangular parallelepiped shape and sub-blocks 36 each having the valve unit 40.
The base block 31 has passages 32 formed at given intervals along the length of the base block 31. Each of the passages 32 extends from the top of the base block 31 toward the bottom thereof. A horizontal main channel 33 is formed along the length of the base block 31 under bottom ends of the passages 32. The passages 32 communicate with the main channel 33 through openings 34 formed on the top wall of the main channel 33. Each end of the main channel 33 has a connection port 35.
The sub-blocks 36 are arranged on the base block 31. A lower part of each sub-block 36 has a vertical passage 37 connected to the top of the passage 32 of the base block 31. A side face of the sub-block 36 has a horizontal intake 38 for receiving a secondary fluid. The intake 38 communicates with the passage 37 through a lower part of the valve unit 40. The valve unit 40 is a known one having the valve element 41 that is moved upward by air and downward by a spring 45. The valve element 41 opens and closes the top of the passage 37. The valve unit 40 has a diaphragm 42. In FIG. 4, the base block 31 has five sub-blocks 36.
The manifold valve 30 is inserted into piping for passing a primary fluid, by connecting the opposite ends of the main channel 33 to the piping. Each of the intakes 38 is connected to a unit for supplying a secondary fluid of chemicals. In the left sub-block 36 of FIG. 6, the valve unit 40 is operated to open the top 37a of the passage 37 so that a secondary fluid containing chemicals of a given quantity is supplied down into the main channel 33 through the passages 37 and 32. Secondary fluids containing chemicals of the sub-blocks 36 may be switched from one to another and be supplied into the primary fluid by selectively opening the tops of the passages 37 with the valve units 40.
In FIG. 6, the length of the base block 31 is cut to have only three sub-blocks 36 so that it corresponds to a manifold valve 10 of FIG. 1 to be explained later. The valve units 40 of FIG. 6 are in different states of supplying secondary fluids. In practice, the valve units 40 operate independently of one another, and therefore, may sometimes operate simultaneously and differently depending on the quantities and supplying timing of secondary fluids.
After supplying the secondary fluid into the main channel 33, the valve unit 40 closes the top 37a of the passage 37 to stop the secondary fluid as in the center sub-block 36 of FIG. 6. In this case, a recess 39 is formed to hold the secondary fluid between the top 37a of the passage 37 and the opening 34. Since the top 37a is closed with the valve element 41, the secondary fluid in the recess 39 stays there due to surface tension and gradually drops into the primary fluid in the main channel 33. As a result, the main channel 33 will provide a fluid with unwanted components for a certain time, even though the user wants the primary fluid pure or having specified composition. In this way, the recess 39 deteriorates the efficacy of supply of a required fluid.
When changing a given primary fluid to another, the latter must be supplied to the main channel 33 for a proper time to wash the inside of the valve units 40. Any fluid in the recesses 39 is hardly removed therefrom because the recesses 39 are deeper than the inner surface of the main channel 33. It takes much time, labor, and fluid to completely wash the remaining fluid out of the recesses 39. This is not economical. In addition, chemicals in the recesses 39 may react and solidify to cause trouble.